Zmodyfikowany pręt Hopkinsona

The aim of this paper is to discuss some possibilities as well as experimental results which are connected with the behaviour of metals at high rates of strain. The complete spectrum of strain rates has been discussed having in mind a variety of experimental techniques in the particular ranges of spectrum. The strain rate spectrum takes into account twelve decimal orders, from 10-6 s^-1 to 10^6 s^-1. In the next part of the paper a more detailed description of the split Hopkinson pressure bar technique is given. In this technique the soft wafer specimen is inserted between two hard bars of the proper length. At the one end of this system the longitudinal elastic wave is developed (incident wave). When the incident wave passes the wafer specimen, the reflected and transmitted waves appear, and the specimen undergoes the plastic deformation. The proper analysis of the oscillographic record enables us to obtain a dynamic strain hardening curve. Some further developments of the technique have been discussed, the torsional method in particular. Finally, the split Hopkinson pressure bar, which was designed and made in the Institute of Fundamental Technical Research, has been shown. The preliminary experimental results for soft aluminium have also been shown.